Is there any open source counterpart to the IBM Watson?
I am not aware of any open-source products that can readily replace IBM Watson, but the following projects could be of interest to you in that regard: 


DARPA DeepDive 
Snorkel
Apache UIMA
YodaQA
OpenCog
OAQA (Open Advancement of Question Answering Systems)
Stanford CoreNLP – Natural language software 
openQA